This invention relates to improvement in two-cycle internal combustion engines.
It is known that in precompression engines the scavenging of burned gases is generally performed using fresh carburetted air, which results in low efficiency and high losses by exhaust. It is well known that this results in a great consumption of fuel and the presence of unburned hydrocarbons in the exhaust gases.
Numerous devices have already been proposed to remedy these drawbacks. These devices generally aim at performing the scavenging of the unburned gases not with fresh carburetted gases but with pure air and introducing the carburetted gases only after scavenging. This is the case, for example, with direct injection engines for which the scavenging air creates an aerodynamic screen in front of the injector. This is also the case in engines which include a balancing piston and in which, for scavenging, pure air, which has been previously compressed by the outside face of the balancing piston, is used, the pure scavenging air being fed into the main cylinder via a transfer port uncovered by the main piston ahead of the intake port coupled to the pump crankcase by which the carburetted gases are then fed into the main, power (drive) cylinder.
There are also known, particularly from British Patent Specification No. 105, 649, engines of this type, in which the pump crankcase supplies scavenging air and the auxiliary cylinder carburetted air. However, in these engines the gas mixture is introduced in the main cylinder after the exhaust and scavenging air intake ports have been closed. This introduction therefore must be performed with a high pressure, able to overcome the counterpressure that already prevails in the cylinder. Introduction of the gas mixture therefore cannot be done under good conditions.